The invention relates to a medical MRI apparatus provided with a patient table having an elongated patient carrier the longitudinal direction of which, if said patient carrier is placed in the imaging volume of the MRI apparatus, coincides with the direction of the stationary magnetic field in the imaging volume, which medical MRI apparatus is provided with at least one device cable for low-frequency electric conduction, which device cable comprises mutually separated segments which are each shorter than a predetermined value, and wherein the segments are separated from each other by frequency-dependent separation elements forming a conductor for low-frequency currents and an insulator for radio-frequency alternating current.
Such an MRI apparatus is known from the published European patent application No. 1 105 966. In this known MRI apparatus, a mobile patient table can be used to take the patient to be examined up to the MRI apparatus. On the patient table there is a patient carrier on which the patient lies. Next, the patient on the patient carrier is moved from the patient table into the imaging volume of the apparatus. In the imaging volume there is a device in the form of a television camera for monitoring the patient during recording the MRI image. The power supply of the television camera takes place via a segmented device cable comprised of segments which are each shorter than ¼ wavelength of the radio-frequency radiation generated in the MRI apparatus to produce the MRI image. The segments are separated from each other by self-inductance elements which, as is known, form a conductor for DC current and low-frequency signals and an insulator for high-frequency signals. In this case, low-frequency signals are to be taken to mean signals having a frequency up to for example 20 kHz, so that they also include audio signals, while high-frequency signals are to be taken to mean signals having a frequency above, for example, 20 MHz. In a typical MRI apparatus with a stationary field of for example 1.5 T, the radio-frequency signal has a frequency of approximately 64 MHz. The self-inductance elements thus form an insulator for the high frequencies and a conductor for the low frequencies. As a result, the cable thus segmented does not cause the antenna for emitting said high frequencies (referred to as RF body coil in an MRI apparatus) to become non-resonant, which would be the case if use were made of an unsegmented cable and hence RF excitation of the tissue to be imaged would no longer take place, so that MRI imaging would be impossible.
It is possible that a patient has to be examined under conditions where he is surrounded by a large number of devices which all require electric power and/or require low-frequency signal exchange with the environment. Apart from television cameras, said devices are, for example, devices for transferring physiologic quantities such as pulse beat, blood pressure, temperature or ECG data to devices for communication, such as audio communication with the patient, and to devices for illumination in the imaging volume of the MRI apparatus. This would result in the presence of a large number of device cables around and over the patient, which is inconvenient for the staff attending the patient and unpleasant for the patient himself.